Alexa, Evan, Koji, Arnaud, Sheila, Rana
The good news is that ALS is quite stable tonight, staying locked for up to 2 hours.
We have been having trouble transitioning to 3F tonight. We can transition MICH and PRCL fine, but we have seen a lot of noise at 300 Hz when we try to transition SRCL to 3F. When we try to transition we see noise at 23.5Hz.
ALS lock loss times: (all Jan 21st UTC) 0:03:02, 0:34:26
ALS lock loss +HEPI, ISI and sus trips: 7:30:15, 5:15:26
Lockloss and bad misalingment of IMC due to DOF4: 6:35
DRMI + arms off resonance lock loss due to SRCL 3f transition at 01/21/14 08:06:00 UTC
Keita, Sheila, Daniel, Alexa
Here is a screen shot of what happened that caused HEPI and ISI trips on DIFF lockloss last night. First, the arms loose the green lock, at that time the DARM output becomes very large, the gaurdian ramps this down over ten seconds, durring which time the integrator in L1 is still integrating. The guardian eventually clears this integrator. Before the integrator was cleared, the arm cavity flashes, although the suspension was still swinging so this produced a momentary lock. The tidal comes on, with a large output because the integrator in L1 has not been cleared yet.
We have done 4 things to help prevent this in the future:
The last thing that we need to do is add a delay to the logic for the tidal feedback, so that it does not engage prematurely on these momentary locks.